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Fft carrier frequency offset estimation for ofdm signal

Active Publication Date: 2009-06-25
NOKIA TECHNOLOGLES OY
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Benefits of technology

[0007]It is therefore an object of the invention to provide a receiver, a mobile station, a sub-assembly, a chipset and a computer program product to reduce the required synchronization time.
[0008]According to the invention, the spectrum shape of the received OFDM signal, which is fast fourier transform (FFT) transformed, can be adapted to indicate the possible carrier frequency offset. Thus, there is no need for the known scanning process. Because the scanning process takes considerable amount of time, the invention achieves considerable savings in reception time. Furthermore the receiver can more directly tune into the desired frequency / channel.
[0010]In another further embodiment an estimator (or so-called one-shot FFT block or also alternatively referred to as one-shot branch or a carrier frequency estimator) outputs a rough frequency offset estimation, which is rather directly available. This allows a direct tuning of the RF modulator of the receiver into the acquisition range of + / −125 kHz. Therefore, no scanning is needed, which saves a considerable amount of time in the signal reception processing in the receiver.

Problems solved by technology

Therefore, no scanning is needed, which saves a considerable amount of time in the signal reception processing in the receiver.

Method used

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  • Fft carrier frequency offset estimation for ofdm signal
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  • Fft carrier frequency offset estimation for ofdm signal

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Embodiment Construction

[0016]A further embodiment of the invention relates to OFDM radio signal reception and especially the channel search during start-up of the receiver. The OFDM signal and the further embodiment are applicable in DVB-T / H system (e.g. terrestrial, wireless, hand held or mobile DVB systems).

[0017]As discussed briefly, FIG. 1 depicts a spectrum scenario (100) without a frequency offset showing guard bands (102) of FFT (Fast Fourier Transform) signal according to some further embodiments of the invention. An algorithm in accordance with some further embodiments is based on detecting the guard-bands (102). The guard bands (102) are clearly shown in FIG. 1. The FFT covers the full FFT range (101) from −4.6 to 4.6 MHz. Therefore it is possible to detect the guard bands (102), which are typically located from −4.2 to −3.8 MHz and 3.8 to 4.2 MHz. A spectrum shape can be prominently shown in the FIG. 1, for example in the receiver filtering (103).

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Abstract

There is being disclosed an OFDM signal receiver for detecting carrier frequency offset. When FFT transform of the signal is processed in the receiver, an estimator applies the spectrum shape of the FFT transform for estimating the carrier frequency offset.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application is for entry into the U.S. national phase under §371 for International Application No. PCT / FI2004 / 000390 having an international filing date of Jun. 28, 2004, and from which priority is claimed under all applicable sections of Title 35 of the United States Code.TECHNICAL FIELD OF THE INVENTION[0002]The present invention concerns a receiver for receiving an OFDM signal. Furthermore, the invention concerns a mobile station, a sub-assembly, a chipset, a computer program and the use of such apparatuses for receiving an OFDM signal.BACKGROUND ART[0003]Multi-carrier signal radio technique such as Orthogonal Frequency Division Multiplexing (OFDM) radio technique is generally used for transmitting quite a lot of data via various frequencies. OFDM can be used in digital broadcasting systems such as DVB system. Environments and situations in the multi-carrier signal systems like broadcasting, which itself has a long history in tele...

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Application Information

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IPC IPC(8): H04L27/28
CPCH04L27/2657H04L27/2685H04L27/2676
Inventor SCHWOERER, LUDWIGKAUFMANN, ANDRE
Owner NOKIA TECHNOLOGLES OY
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